Answers Database
PACKAGES: Information on calculating Temperature/Thermal Characteristics (Theta-JA)
Record #1226
Product Family: Documentation
Product Line: Data Book
Product Part: Programmable Logic Data Book
Problem Title:
PACKAGES: Information on calculating Temperature/Thermal Characteristics (Theta-JA)
Problem Description:
Urgency: Standard
General Description:
This is a brief summary on determining the thermal characteristics of a Xilinx Part. A more detaile
d discussion of thermal characterization can be found in the chapter called "Packages and Thermal Ch
aracteristics"
usually located in the last sections of the data book.
Solution 1:
Theta-JA (junction-to-ambient heat resistance) is used to calculate the die temperature, which shoul
d not exceed the maximum temperature rating for a particular device. Theta-JA is the increase in te
mperature that a device will experience, relative to the ambient temperature, over the amount of pow
er dissipated by the device (degrees Celsius per watt). In short, the following equation must hold:
Ta + P*Theta-JA < Tj
where Ta is ambient temperature, P is the power dissipated by the device, and Tj is the maximum temp
erature rating for the device (85C commercial, 100C industrial, Tc=125C for military).
We measure Theta-JA in four different situations:
0 LPM (still air)
250 LPM (air flow of 250 linear feet per minute)
500 LPM ( " " " 500 " " " " " " " )
750 LPM ( " " " 750 " " " " " " " )
You can therefore use the measurement or measurements that fit your particular situation.
Note: For most devices the temperature range for Military
grade devices (M and B) is the case temperature not the
junction temperature. For further information on a
partitcular device please check the Xilinx Programmable
Logic Databook.
End of Record #1226 - Last Modified: 03/02/98 11:37 |
